Apparatus for the treatment of pigments



Nov. 26, 1935. "H. A; DEPEW APPARATUS FOR- THE TREATMENT OF PIGMENTS Original Filed- June 19, 19:53

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, ence numerals indicate like parts throughout the Patented Nov. 26, 1935 PATENT OFFICE APPARATUS FOR THE TREATMENT-F PIGMENTS Harlan A. .Depew, Columbus, Ohio, to American Zinc, Lead & smelting Company,

St. Louis, Mo., a corporation of Maine Original application June 19, 1933, Serial Nob,

Divided and this application Novembet 2,1933, Serial No. 696,442 I 4 6 Claims. (01-23-277) This invention relates to furnaces or mufllers for the treatment of pigments and is a division of my application Serial No. 676,590, filed June 19, 1933. When zinc sulphide pigment, for example, is made by the reaction of zinc vapor and sulphur vapor, the product may contain some free sulphur, zinc and zinc oxide and even some carbon,-as wellas some absorbed tars and gases.

Furthermore, the particle size may be so fine as to be undesirable for some uses.

The object of the present invention is to provide a mufliing furnace capable of being operated to remove various impurities from certain classes of pigments and, if desired, increasing the particle size of the pigment, all without subjecting the pigment to the actionof moisture.

The inventive idea is capable of being embodied in a variety of forms, two of which are illustrated in the "accompanying drawings, but such drawings are to be understood as illustrations only, and not as defining the limits of the invention, reference being had tofthe appended claims for this purpose.

' In said drawings:

Fig. 1 is a. diagrammatic view of an apparatus for continuouslypassing pigment first through a mufiling furnace and thence'onward through a cooler from which it'is delivered into a suitable bin.

Fig. 2 is a diagrammatic view ofa modification reheat of the pigment after it passes through the muflie proper and before it is subjected to the action of the cooler.

Referring to the drawings, in which like referseveral views, and first to Fig. 1, reference numeral I indicates any source of pigment, as a hopper, into which the pigment may be fed in the-usual or any suitable manner; 2 indicates a closed conduit within which operates a power-- driven screw 2", and the hopper I delivers the pigment into-the conduit 2 along which it is advanced by the screw 2'. A suitable furnace 3 surrounds a portion of the conduit 2, and'.thuseffects the heating of that-portion of the con-. duit within the furnace and of the pigment during the time it is being advanced through the furnace 3. vAs here shown, the upper portion of in which provision is madeior effecting a soaking,

ment leaves the furnace 3, the screw 2 has a portion of the thread omitted, and by the. operation of the apparatus the pigment packsat the points 5 and 6. leaving a space H betweemsaid points and within the furnace through which the pigment is advanced'by the screw, but without entirely filling the space. Immediately beyond the pointii in the conduit 2, the said conduit is surrounded by -a suitable water jacket I I for quickly cooling the pigment as it passes through said jacket. Water is admitted into the chamber through the inlet 8, and by reason of the temperature within said chamber (400 C.900

C. depending on individual considerations) this water is immediately converted into gas at high pressure, which gas comes in contact with the pigment as it passes through the chamber. II and then leaves said chamber through the exhaust 9. Other suitable inert gas or gases, such as CO2, that is reactive with carbon, or non-oxidiz- I exit end thereof. Such exit of the gas at either one of' these points into the cooler parts of the conduit 2 would result in a condensation 'of moisture on the pigment within/the conduit 2. The

packed masses of pigment at the points ii and 6 constitute seals to prevent this exit of the vapor from the chamber II at these points.- In some cases it is desirable to reenforce the pigment seals by introducing inert gas under pressure into the conduit 2, to the rear of. thepigment seal 5 and in advance of the pigment seal 6, throug 3;

suitable inlets I0 and I2. The pressure of thijs inert gas is so adjusted as to effectively prevent the exit of the water vapor from the fumace 3 and its consequent c0ndensation-in the form of moisture on the pigment on the exterior of the 40 seal at 5.

The thread maybe'removed from the screw 2' at the point "I just beyond the'cooler I I, thus forming a pigment seal at this point for the inert gas that enters the conduit 2 at I 2. The packing of the pigment in the hopper. I enables the pres-' sure of the gas entering at point I9 to be maintained at that point. After the pigment passes the cooler I4 and the seal at point I, it is discharged into asuitable container 4 from which 3.

it may be removed either periodically or continuously from the bottom.

In some cases a chemical that will act to produce gas pressure may be added to the pigment being treated before it reaches the seal and the gas pressure thus secured will help in maintaining the seal at said point. Thus, for example, when zinc sulphide pigment is being treated in the muilier, sulphur may be added to the zinc sulphide and when the pigment enters the heatingzone at 5, one of the reactions that takes place is and the SO: aids in maintaining the seal at the point 5. Inert gas that may be introduced at point 10, if found necessary, enables the pressure to be maintained at the rear of seal-point 5 equal to or slightly superior to the pressure in I I, and thus prevents the water vapor from pass mg from H to the rear of seal 5 and being condensed upon the pigment, and thus the vapor or other inert gas in the chamber II is forced to leave at the exit point 9, together with the excess sulphur vapor, 80 2, and absorbed gases.

The water jacket l4 makes it possible to rapidly cool the pigment. If the sole purpose of the heating is to refine the pigment by removing impurities therefrom, a relatively low temperature and short time before cooling is sufficient, but if it is to be desired to increase the size of the particles a higher temperature and a longer time in the heated conduit may prove desirable. Fig. 2 is a diagrammatic view of a modified. form of the apparatus that is particularly serviceable for this purpose. The arrangement in this figure is essentially the same as in Fig. 1 except that the screw 2' discharges the pigment into a tall tower l| constituting a continuation of the conduit, a sliding screen l5 causing the pigment to fall in a dispersed cloud through the upper portion H, where the reactions of theimpurities with the water vapor or other gas and the distillation of impurities is completed. Preferably the up per portion ll of the tower I1 is enclosed in a 45 downward extension 3' of the furnace 3, and the lower portion of the tower is suitably insulated, as at I8. The hot pigment is'allowed to collect at I6 in the bottom portion of the tower. A second screw 2| continuously advances the pigment from the bottom of the tower past theseal a, through the cooler M, and past the seal 1, and deposits it in the bin. The upper portion ll of the tower I1 is maintained at a temperature 55 above 100 0., and preferably from 400 C. to 900 C. and this immediately converts the water entering at 8' into dry steam which passes downward through the falling .pigment and out through the exit 9'. Owing to the high tem- 6o perature of the pigment no steam condenses as moisture thereon and the hot pigment at l6 thus remains in the same dry condition in which it wasbefore treatment.

The apparatus is so operated that the hot pigment in the insulated bottom portion of the tower is always at a considerable depth, as shown in Fig. 2, with the result that the pigment is retained in-its highly heated condition (400 C. to 900 C.) and in anlnert atmosphere for a considerable time. This is technically known as, and is herein referred to as, a soaking reheat". Such a soaking reheat results in a material growth or increase in size of the pigment particles and is only resorted to when such 111,-.

75 crease is desired.

It will be readily appreciated that either of the forms of apparatus shown can be operated at a relatively low temperature and the pigment exposed thereto for a short period of time required when it is merely desired to refine the pigment 5 by the removal ofimpurities; or, if it is desired to increase the size of or grow the particles (and perhaps remove impurities) a higher temperature may be employed and the pigment remain under treatment for a longer period of time, 10 as may be desired.

It will also be understood that the apparatus may be employedin the treatment of such pigments as lithopone, zinc sulphide and zinc oxide made in a wet way and dried and disintegrated 15 before introduction into the hopper. Moreover, the bin 4 may be omitted and the pigment discharged directly' into the air.

What is claimed is:---

1. In a mufiiing apparatus, the combination of means supplying material to be treated, a cooler,

a. conduit extending from said supply means to and through the cooler, a furnace between said supply means and cooler and surrounding a portion of said conduit, screw means extending into the furnace and advancing material to be treated from said supply means along said conduit and through said cooler, said screw means having 'a portion of the screw thread omitted adjacent the points where the conduit enters said furnace and cooler, whereby gas seals are eifected by the material under treatment, and said conduit being provided with an entranceand an exit for gaseous material between said seals.

2. In a mufliing apparatus, the combination of means supplying material to be treated, a cooler,

a conduit extending from said supply means to and through the cooler, a furnace between said supply means and cooler and surrounding a portion of said conduit, screw means extending into the furnace and advancing material to be treated from said supply means along said conduit and through said cooler, said screw means having a portion of the screw thread omitted adiacent the points where the conduit enters said furnace and 45.

. material between said seals, and a soaking reheat chamber forming a part of said conduit and located between said furnace and the exit seal.

3. In a muflling apparatus, the combination of a furnace, means supplying material to be treated at one side of said furnace, a cooler at the other side thereof, a conduit extending from said supply means through said furnace and said cooler, said conduit having an enlarged portion within the furnace, a screw in said conduit extending from said supply means to and through the furnace and advancing the material to be treated from said supply means through said conduit, said screw having a portion of its thread omitted adjacent the points where it enters and leaves said furnace and cooler, whereby gas 'seals are formed by the material, and said enlarged portion of the conduit being provided with an entrance and an exit for gaseous material between said seals.

4. In a mufliing apparatus, the combination of means supplying, material to be treated, a cooler, acontinuous conduit from said supply means through said cooler, a furnace between the supply means and the cooler and serving to heat said conduit, a two part screw means, one part exby gas seals are elected, by the material under tending into the furnace and advancing the material into the furnace and the other part extending through and advancing the material throughthe cooler, said screw means having a portion of the screw thread omitted adjacent the entrance to the fuma'ce and adjacent the entrance 'to the cooler, whereby gas seals are formed by the material at said points, and an entrance and an exit for gaseous material into said con- .duit between said seals.

and extending through the furnace and cooler,

said screw means having portions of the screw thread omitted at points within the furnace where the conduit enters and leaves the furnace, wheretreatment, and said conduit being provided with an entrance and an exit for gaseous material between said seals.-

6. In a mun'ling apparatus, the combination of means supplying material to be treated, a cooler, a cylindrical conduit extending from said supply means to said cooler, a furnace between said sup- Ply means and cooler and surrounding a portion of the conduit, said conduit having an upper en- 10 largement within the furnace, screw means'in said conduit and extending through the furnace to the cooler, said screw means having portions of the screw thread; omitted at points within the furnace where the conduit enters and leaves the 15 furnace, whereby gas seals are effected by the material under treatment, and said conduit being provided with an entranceandan exit for gaseous material in said enlargement.

' HARLAN A. DEPEW. 20 

